1. Field of the Invention
The present invention relates to control circuitry used for timing the firing of wide spanning hammers and in particular, to wide spanning hammers capable of operating in more than one printing mode, e.g., as double or triple spanning hammers.
2. Description of the Prior Art
In the prior art, multiple spanning hammers, such as double or triple spanning hammers, are fired by complex circuitry using logically controlled one shot pulse generators or complex schemes for adding phase delays. Such prior art circuitry is not only complex and expensive to construct and to maintain, but is ill-adapted to operation in multiple modes of operation. In addition, such prior art control circuitry is unable to track significant font speed variations and requires complex adjustments in order to remain calibrated to a given font speed. Furthermore, prior art control circuitry for impact hammers operable both as double and triple spanning hammers is cumbersome and requires complex circuit design requiring a substantial degree of circuit replication.
The present invention overcomes each of these disadvantages found in the prior art and allows a font position and timing circuit to be easily and inexpensively fabricated which will track font speeds and be capable of operating in a plurality of print modes, such as both double and triple spanning hammer operations.